diff --git a/app.go b/app.go
index 307c2dc..e71d8b3 100644
--- a/app.go
+++ b/app.go
@@ -16538,7 +16538,72 @@ type WinkeyerSettings struct {
 
 // ListSerialPorts returns the available COM ports for the keyer dropdown.
 func (a *App) ListSerialPorts() ([]string, error) {
-	return winkeyer.ListPorts()
+	ports, err := winkeyer.ListPorts()
+	if err != nil {
+		return nil, err
+	}
+	return tidySerialPorts(ports), nil
+}
+
+// tidySerialPorts removes duplicates and puts the list in the order a human
+// reads it.
+//
+// Windows enumerates serial ports from HARDWARE\DEVICEMAP\SERIALCOMM, which maps
+// a DEVICE path to a COM name — so the same name legitimately appears twice when
+// two devices claim it. That happens with a driver uninstalled without cleaning
+// up after itself, and with virtual-port software. An operator saw COM1 and COM3
+// listed twice, and the dropdown showed "COM3COM3" as its value, because two
+// entries with the same value both counted as selected.
+//
+// The order is natural, not lexical: COM4 belongs between COM3 and COM8, and
+// listing it after COM9 is how a port gets overlooked on a machine with a dozen.
+// Anything not named COMn keeps its own alphabetical order, after them.
+//
+// A duplicate is worth a log line rather than silence: two devices holding one
+// COM name is also why one of them is "busy" when the other is opened, and that
+// is not something an operator can work out from a dropdown.
+func tidySerialPorts(ports []string) []string {
+	seen := make(map[string]bool, len(ports))
+	out := make([]string, 0, len(ports))
+	for _, p := range ports {
+		name := strings.TrimSpace(p)
+		if name == "" {
+			continue
+		}
+		key := strings.ToUpper(name)
+		if seen[key] {
+			applog.Printf("serial: %s is claimed by more than one device in the Windows port map — listing it once", name)
+			continue
+		}
+		seen[key] = true
+		out = append(out, name)
+	}
+	sort.SliceStable(out, func(i, j int) bool {
+		ni, oki := comPortNumber(out[i])
+		nj, okj := comPortNumber(out[j])
+		switch {
+		case oki && okj:
+			return ni < nj
+		case oki:
+			return true // COMn before anything else
+		case okj:
+			return false
+		}
+		return out[i] < out[j]
+	})
+	return out
+}
+
+// comPortNumber extracts n from "COMn", false for any other shape.
+func comPortNumber(s string) (int, bool) {
+	if len(s) <= 3 || !strings.EqualFold(s[:3], "COM") {
+		return 0, false
+	}
+	n, err := strconv.Atoi(s[3:])
+	if err != nil {
+		return 0, false
+	}
+	return n, true
 }
 
 // GetWinkeyerSettings returns the persisted keyer config (with sane defaults).
diff --git a/changelog.json b/changelog.json
index 7f80a16..9f1efe9 100644
--- a/changelog.json
+++ b/changelog.json
@@ -5,12 +5,14 @@
     "en": [
       "Send Spot: the comment now carries the award references after the mode — the ones you assigned (POTA, SOTA, IOTA…), not the DXCC, zone and prefix every reader works out from the callsign. A self-spot carries your OWN activation references instead.",
       "Modes: a fresh install now starts with SSB, CW, FT8, FT4, FT2, RTTY, PSK31 and FM. AM and DIGITALVOICE stay in the available list but are no longer selected by default.",
-      "Chase new: a panel listing the stations PSK Reporter is hearing within about 300 km of you that are new against your log — entity, band, mode, slot, prefix or square. Click one to put it in the entry and tune the rig. Digital modes only, and it shares the feed the band-opening watch and the locator store already use."
+      "Chase new: a panel listing the stations PSK Reporter is hearing within about 300 km of you that are new against your log — entity, band, mode, slot, prefix or square. Click one to put it in the entry and tune the rig. Digital modes only, and it shares the feed the band-opening watch and the locator store already use.",
+      "Serial ports: a port claimed by two devices in the Windows port map was listed twice in every port dropdown, and showed as “COM3COM3”. Listed once now, and in natural order — COM4 between COM3 and COM8, not after COM9."
     ],
     "fr": [
       "Envoi de spot : le commentaire porte désormais les références de diplôme après le mode — celles que vous avez attribuées (POTA, SOTA, IOTA…), pas le DXCC, la zone et le préfixe que chacun déduit de l’indicatif. Un auto-spot porte VOS références d’activation.",
       "Modes : une installation neuve démarre avec SSB, CW, FT8, FT4, FT2, RTTY, PSK31 et FM. AM et DIGITALVOICE restent dans la liste disponible mais ne sont plus sélectionnés par défaut.",
-      "Chasse au nouveau : un panneau listant les stations que PSK Reporter entend à moins de 300 km de chez vous et qui sont nouvelles par rapport à votre log — entité, bande, mode, créneau, préfixe ou carré. Un clic la met en saisie et accorde la radio. Modes numériques uniquement, et le flux est partagé avec la veille d’ouvertures et la base des locators."
+      "Chasse au nouveau : un panneau listant les stations que PSK Reporter entend à moins de 300 km de chez vous et qui sont nouvelles par rapport à votre log — entité, bande, mode, créneau, préfixe ou carré. Un clic la met en saisie et accorde la radio. Modes numériques uniquement, et le flux est partagé avec la veille d’ouvertures et la base des locators.",
+      "Ports série : un port revendiqué par deux périphériques dans la table Windows apparaissait en double dans toutes les listes, et s’affichait « COM3COM3 ». Une seule fois désormais, et dans l’ordre naturel — COM4 entre COM3 et COM8, pas après COM9."
     ]
   },
   {
diff --git a/serialports_test.go b/serialports_test.go
new file mode 100644
index 0000000..f64010e
--- /dev/null
+++ b/serialports_test.go
@@ -0,0 +1,46 @@
+package main
+
+import (
+	"strings"
+	"testing"
+)
+
+// The exact list an operator's machine produced: COM1 and COM3 each claimed by
+// two devices in the Windows port map, and no order to speak of. The dropdown
+// showed every duplicate, and rendered its own value as "COM3COM3" because two
+// entries with the same value both counted as selected.
+func TestTidySerialPortsDeduplicatesAndOrders(t *testing.T) {
+	got := tidySerialPorts([]string{"COM1", "COM1", "COM3", "COM8", "COM9", "COM4", "COM3"})
+	want := []string{"COM1", "COM3", "COM4", "COM8", "COM9"}
+	if strings.Join(got, ",") != strings.Join(want, ",") {
+		t.Errorf("got %v, want %v", got, want)
+	}
+}
+
+// COM10 after COM9, not between COM1 and COM2 — lexical order is how a port
+// gets overlooked on a machine with a dozen of them.
+func TestTidySerialPortsSortsNaturally(t *testing.T) {
+	got := tidySerialPorts([]string{"COM10", "COM2", "COM1", "COM20", "COM3"})
+	want := []string{"COM1", "COM2", "COM3", "COM10", "COM20"}
+	if strings.Join(got, ",") != strings.Join(want, ",") {
+		t.Errorf("got %v, want %v", got, want)
+	}
+}
+
+// Not every port is a COMn: a device path or a Unix name must survive, after
+// the numbered ones, in its own order.
+func TestTidySerialPortsKeepsOtherNames(t *testing.T) {
+	got := tidySerialPorts([]string{"/dev/ttyUSB1", "COM3", "/dev/ttyUSB0", "COM1", "", "  "})
+	want := []string{"COM1", "COM3", "/dev/ttyUSB0", "/dev/ttyUSB1"}
+	if strings.Join(got, ",") != strings.Join(want, ",") {
+		t.Errorf("got %v, want %v", got, want)
+	}
+}
+
+// Case is not identity on Windows: "com3" and "COM3" are one port, and letting
+// both through would put the same duplicate back in the list.
+func TestTidySerialPortsIgnoresCase(t *testing.T) {
+	if got := tidySerialPorts([]string{"COM3", "com3"}); len(got) != 1 || got[0] != "COM3" {
+		t.Errorf("got %v, want [COM3]", got)
+	}
+}